Conventionally, a method called RNAi (RNA interference), where transcription is repressed by cutting target mRNA in a double-stranded RNA, has been known. Usually, RNAi involves base length of about 20 base pairs and a screening method for its double-stranded oligonucleotide and antisense RNA has been disclosed (Patent Document 1: Japanese Patent Application Laid-Open No. 2005-13224).
Also, compounds useful in controlling interleukin genes, interleukin superfamily genes, expression of genes and/or expression and activities of genes involved in interleukin routes of activities, by RNA interference (RNAi) using small nucleic acid molecules such as short interfering nucleic acid (siNA), short interfering RNA (siRNA), double-stranded RNA (dsRNA), microRNA (miRNA), and short hairpin RNA (shRNA) molecules have been disclosed (Patent Document 2: Japanese Patent Application Laid-Open No. 2005-524393).
If antisense RNA exists in a cell, gene expression can be inhibited by hybridizing with complementary mRNA to inhibit translation from mRNA to proteins. If antisense RNA is artificially introduced into a cell, expression of target gene can be inhibited. Therefore, this technique is currently used as a technique shedding light on gene functions and its application into medicinal products has been studied. However, there are many unknown points in what mode RNA exists in a cell and therefore there are many points unclear as to controlling of its expression with transcription process from mRNA to protein as target.                [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-13224        [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-524393        